1. Field of the Invention
The present invention relates to a strip connecting apparatus and method for connecting end portions of strips with each other by a seam welding method, and more particularly to a technology for overlapping end portions of strips one on another in which an insulation coating such as a scale coating, a plated layer or an insulative surface coating such as a surface coating layer is present on the surfaces of the strips for the seam welding.
2. Description of the Related Art
In order to weld in a stable manner the strips in which the insulative surface coating is present, it is necessary to remove the insulative surface coating. As a method for removing the insulative surface coating, there are known examples as follows.
(1) In the case where oxidized coating is present in welding material, it is removed by polishing the surface with a wire brush (see Japanese Patent Application Laid-Open No. Hei 5-104252 et al.)
(2) In the case where the laminate steel plate is welded, the resin coating on the surface of the steel plate is removed (see Japanese Patent Application Laid-Open No. Hei 5-177764).
(3) As a means for removing the applied coating of the coated steel plate, it is possible to use a thermal means with a high energy density beam such as a laser beam or an electron beam. For instance, it is possible to use a chemical means such as chemical agent or plasma or a mechanical means such as a grinder, a file or a sandblast or the like (Japanese Utility Model Application Laid-Open No. Hei 1-80277).
As apparent from these known examples, it is difficult to perform the welding method for the material in which the coating is present on the surface. It is a task how the coating is removed.
A flash welding method or an arc welding method such as MIG or TIG has been used for bonding the strips after the hot pressing process also in the steel process line, for example. (According to these welding methods, it is possible to perform the welding without any adverse affect on the insulative surface coating (see Japanese Patent Application Laid-Open No. Hei 3-52778).
However, these welding methods suffer from problems that, for example, the apparatus is expensive and the welding time is long. Therefore, in order to solve these problems, a welding method for a steel split has been proposed (Japanese Patent Application Laid-Open No. Hei 3-52778).
The Japanese Patent Application Laid-Open No. Hei 3-52778 discloses a method in which the respective leading steel strip (leading coil) and the trailing steel strip (trailing coil) which are overlapped one on another are depressed by a pressure down roller (swaging roll) and the insulation coating such as a scale coating or the like is removed by the working heat that occurs during this process.
However, according to this method, since the welding is completed under the condition that the scale of the weld bond portion is rolled in, it is impossible to ensure the welding quality in a stable manner.
Also, as a method for removing the surface coating on the strip, the method shown in FIGS. 16 and 17 are known. FIG. 16 shows a method in which, after strips 1a and 1b have been cut, upper and lower pairs of brushes 11, 12; 13, 14 are brought into contact with upper and lower surfaces of the strips 1a and 1b, respectively, to thereby remove the surface coating. If the brushing is repeated, as shown in FIG. 17, there is a problem in that an outer circumferential portion of the disc-like brushes 11 to 14 is locally abraded and it is impossible to perform the surface coating process in a stable manner. Namely, as shown in FIG. 17 on an enlarged scale, when the edges of the strips 1a and 1b are brushed, the brushes 11 to 14 are locally worn so that stepped portions are generated in the brushes 11 to 14. As a result, in some cases, edge portions A of the upper brushes 11 and 12 and the lower brushes 13 and 14 which have not been abraded are brought into contact with each other so that the strip surfaces that are to be abraded are not abraded.
Furthermore, FIG. 18 shows an example in which after the cut of the strips, the end portions of the two strips are brought into abutment against each other, and under this condition, the surface coating is to be removed by a pair of upper and lower disc-like brushes 41 and 42. As shown in FIG. 19, in the case where there is difference in thickness of the two strips 1a and 1b to be bonded, there is a problem in that the surface coating on one strip 1b (thinner strip) could not be removed.
Accordingly, in order to overcome the above-noted difficulties inherent in the conventional cases, an object of the present invention is to provide a strip connecting apparatus and a method therefor which are less costly, short in welding time and high in welding quality.
In order to attain the above-described object, a strip connecting apparatus according to the present invention is provided with a surface coating removing device for removing insulative surface coating of end portions, to be welded, of a leading strip and a trailing strip before cutting the strips, a cutting device for cutting the end portions, to be welded, of the leading strip and the trailing strip and a welding device for overlapping the cut end portions of the leading strip and the trailing strip and seam welding the cut end portions with each other.
Also, according to one embodiment of the present invention, the cutting device for cutting the end portions, to be welded, of the leading strip and the trailing strip, respectively, is a rotary shear.
Furthermore, according to another embodiment of the present invention, the cutting device for cutting the end portions, to be welded, of the leading strip and the trailing strip, respectively, is a guillotine shear.
Furthermore, according to still another embodiment of the present invention, the surface coating removing device for removing the insulative surface coating of the end portions, to be welded, of the leading strip and the trailing strip comprises a first removing device for removing the insulative surface coating of the leading strip and a second removing device for removing the insulative surface coating of the trailing strip, and the first removing device and the second removing device are installed independently of each other.
Also, according to still another embodiment of the present invention, the surface coating removing device and the welding device are provided on a common carriage that may move on a common base.
Furthermore, according to still another embodiment of the present invention, the surface coating removing device for removing insulative surface coating of the end portions, to be welded, of the leading strip and the trailing strip is composed of a rotary tool having a polishing surface for coming into contact with the surfaces of the leading strip and the trailing strip, and for cutting, and the polishing surface of the rotary tool is automatically controlled to be kept at a constant position relative to the surfaces of the leading strip and the trailing strip.
Furthermore, according to still another embodiment of the present invention, a rotary shaft of the rotary tool is arranged in parallel with the surfaces of the leading strip and the trailing strip, and an outer circumferential portion of the rotary tool is brought into contact with the surface of the leading strip and the trailing strip.
Also, according to still another embodiment of the present invention, a rotary shaft of the rotary tool is arranged to be slanted relative to a line vertical to the surfaces of the leading strip and the trailing strip, and an outer circumferential portion of the rotary tool is brought into contact with the surface of the leading strip and the trailing strip.
Furthermore, according to still another embodiment of the present invention, the cutting device is provided so as to be movable on a common base independently of a carriage that is movable on the common base and on which the welding device is mounted.
Also, according to still another embodiment of the present invention, the cutting device is provided on a common carriage that is movable on the common base and on which the welding device is mounted.
Furthermore, according to still another embodiment of the present invention, a dressing device for cutting a surface of a welding electrode of the welding device is further provided.
Also, a strip connecting method according to the present invention is comprised of the following steps of: removing surface coating of end portions, to be welded, of a leading strip and a trailing strip before cutting the strips; cutting the end portions, to be welded, of the leading strip and the trailing strip after removing the surface coating; and overlapping the cut end portions of the leading strip and the trailing strip and seam welding the cut end portions with each other.
Furthermore, according to still another embodiment of the present invention, the step of overlapping the cut end portions of the leading strip and the trailing strip and welding the cut end portions with each other, is comprised of: a plate alignment step for overlapping the cut end portions of the leading strip and the trailing strip; an overlap adjustment step for adjusting an overlap of the overlapped cut end portions of the leading and trailing strips; and a welding step for seam welding the overlapped cut end portions of the leading strip and the trailing strip with each other.
According to still another embodiment of the present invention, the strip connecting method is further comprised of: after the welding step, a dressing step for cutting the surface of the welding electrode for performing the seam welding operation.